Pixel location calibration image capture and processing

ABSTRACT

What is disclosed are systems and methods for optical correction for correcting for non-uniformity in active matrix light emitting diode device (AMOLED) and other emissive displays, using iterative processing of images of calibration patterns including features of coarse and fine granularity to successively generate a high-resolution estimate of the panel pixel locations.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/999,184, filed Aug. 21, 2020, now allowed, which claims the benefitof U.S. Provisional Patent Application No. 62/891,090, each of which arehereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

The present disclosure generally relates to optical measurement andcalibration of light emissive visual display technology, andparticularly to panel pixel location calibration for optical correctionsystems of active matrix organic light emitting diode device (AMOLED)and other emissive displays.

BRIEF SUMMARY

According to a first aspect there is provided an optical correctionmethod for correcting display of images on a display panel havingpixels, each pixel having a light-emitting device, the methodcomprising: arranging a camera in front of the display panel; displayingone or more calibration patterns on the display panel while capturingone or more calibration images of said calibration patterns with saidcamera, said one or more calibration patterns comprising a spacedpattern of coarse features and a spaced pattern of fine features, aspacing of the coarse features larger than a spacing of the finefeatures; generating a coarse estimate of panel pixel locations withinthe calibration images from the images of the coarse features in thecalibration images; locating images of the fine features within thecalibration images with use of the coarse estimate; generating ahigh-resolution estimate of panel pixel locations within the calibrationimages from the located images of the fine features in the calibrationimages, the high-resolution estimate having greater accuracy than thecoarse estimate; and generating correction data for correcting imagesdisplayed in the display panel with use of the high-resolution estimate.

In some embodiments, the one or more calibration patterns comprises asingle calibration pattern, and wherein the once or more calibrationimages comprises a single image.

In some embodiments, the coarse features are spaced apart from aperiphery of the one or more calibration patterns. In some embodiments,the fine features are distributed throughout the one or more calibrationpatterns. In some embodiments, each fine feature includes pixels of aforeground color, and each coarse feature includes pixels of aforeground color surrounded by an area of a background color, said areaabsent other coarse features or fine features.

In some embodiments, the coarse estimate comprises a first 2D polynomialfunction, the high-resolution estimate comprises a second 2D polynomialfunction, and the second 2D polynomial function has an order greaterthan an order of the first 2D polynomial function.

In some embodiments, said generating the coarse estimate includes:locating images of the coarse features in the one or more calibrationimages; identifying the coarse features of the one or more calibrationpatterns corresponding to said images of the coarse features; andgenerating a coarse mapping between panel pixel locations andcalibration image pixel locations from locations of the images of thecoarse features in the one or more calibration images and knownlocations of the coarse features in the one or more calibrationpatterns, said locating images of the fine features includes: estimatingexpected locations of images of the fine features within the one or morecalibration images with use of the coarse estimate and known locationsof the fine features in the one or more calibration patterns, and saidgenerating the high-resolution estimate includes: identifying the finefeatures of the one or more calibration patterns corresponding to saidimages of the fine features; and generating a high-resolution mappingbetween panel pixel locations and calibration image pixel locations fromlocations of the images of the fine features in the one or morecalibration images and known locations of the fine features in the oneor more calibration patterns.

In some embodiments, identifying the fine features of the one or morecalibration patterns corresponding to said images of the fine featuresincludes: for each expected location of an image of a fine feature,determining the closest image of a fine feature in the one or morecalibrations images which falls within a distance threshold.

In some embodiments, the one or more calibration patterns comprises asingle calibration pattern and the once or more calibration imagescomprises a single image, wherein the coarse features are spaced apartfrom a periphery of the one or more calibration patterns and include asingle pixel of a foreground color surrounded by a square area of abackground color, said square area absent other coarse features or finefeatures, wherein the fine features are distributed throughout thesingle calibration pattern and each fine feature includes a single pixelof a foreground color, and wherein the coarse estimate comprises a first2D polynomial function, the high-resolution estimate comprises a second2D polynomial function, and the second 2D polynomial function has anorder greater than an order of the first 2D polynomial function.

In some embodiments, said generating the coarse estimate includes:locating images of the coarse features in the single calibration image;identifying the coarse features of the single calibration patterncorresponding to said images of the coarse features; and generating acoarse mapping between panel pixel locations and calibration image pixellocations from locations of the images of the coarse features in thesingle calibration image and known locations of the coarse features inthe single calibration pattern, said locating images of the finefeatures includes: estimating expected locations of images of the finefeatures within the single calibration image with use of the coarseestimate and known locations of the fine features in the singlecalibration pattern, and said generating the high-resolution estimateincludes: for each expected location of an image of a fine feature,determining the closest image of a fine feature in the singlecalibration image which falls within a distance threshold to identifythe fine features of the single calibration pattern corresponding tosaid images of the fine features; and generating a high-resolutionmapping between panel pixel locations and calibration image pixellocations from locations of the images of the fine features in thesingle calibration image and known locations of the fine features in thesingle calibration pattern.

According to a second broad aspect there is provided an opticalcorrection system for correcting display of images on a display panelhaving pixels, each pixel having a light-emitting device, the systemcomprising: a camera arranged in front of the display panel; an opticalprocessing circuit coupled to said camera adapted to: display one ormore calibration patterns on the display panel while capturing one ormore calibration images of said calibration patterns with said camera,said one or more calibration patterns comprising a spaced pattern ofcoarse features and a spaced pattern of fine features, a spacing of thecoarse features larger than a spacing of the fine features; generate acoarse estimate of panel pixel locations within the calibration imagesfrom the images of the coarse features in the calibration images; locateimages of the fine features within the calibration images with use ofthe coarse estimate; generate a high-resolution estimate of panel pixellocations within the calibration images from the located images of thefine features in the calibration images, the high-resolution estimatehaving greater accuracy than the coarse estimate; and generatecorrection data for correcting images displayed in the display panelwith use of the high-resolution estimate.

In some embodiments, the optical processing circuit is adapted togenerate the coarse estimate by: locating images of the coarse featuresin the one or more calibration images; identifying the coarse featuresof the one or more calibration patterns corresponding to said images ofthe coarse features; and generating a coarse mapping between panel pixellocations and calibration image pixel locations from locations of theimages of the coarse features in the one or more calibration images andknown locations of the coarse features in the one or more calibrationpatterns, and the optical processing circuit is adapted to locate imagesof the fine features by: estimating expected locations of images of thefine features within the one or more calibration images with use of thecoarse estimate and known locations of the fine features in the one ormore calibration patterns, and the optical processing circuit is adaptedto generate the high-resolution estimate by: identifying the finefeatures of the one or more calibration patterns corresponding to saidimages of the fine features; and generating a high-resolution mappingbetween panel pixel locations and calibration image pixel locations fromlocations of the images of the fine features in the one or morecalibration images and known locations of the fine features in the oneor more calibration patterns.

In some embodiments, the optical processing circuit is adapted toidentify the fine features of the one or more calibration patternscorresponding to said images of the fine features by: for each expectedlocation of an image of a fine feature, determining the closest image ofa fine feature in the one or more calibrations images which falls withina distance threshold.

In some embodiments, the optical processing circuit is adapted togenerate the coarse estimate by: locating images of the coarse featuresin the single calibration image; identifying the coarse features of thesingle calibration pattern corresponding to said images of the coarsefeatures; and generating a coarse mapping between panel pixel locationsand calibration image pixel locations from locations of the images ofthe coarse features in the single calibration image and known locationsof the coarse features in the single calibration pattern, the opticalprocessing circuit is adapted to locate images of the fine features by:estimating expected locations of images of the fine features within thesingle calibration image with use of the coarse estimate and knownlocations of the fine features in the single calibration pattern, andthe optical processing circuit is adapted to generate thehigh-resolution estimate by: for each expected location of an image of afine feature, determining the closest image of a fine feature in thesingle calibration image which falls within a distance threshold toidentify the fine features of the single calibration patterncorresponding to said images of the fine features; and generating ahigh-resolution mapping between panel pixel locations and calibrationimage pixel locations from locations of the images of the fine featuresin the single calibration image and known locations of the fine featuresin the single calibration pattern.

The foregoing and additional aspects and embodiments of the presentdisclosure will be apparent to those of ordinary skill in the art inview of the detailed description of various embodiments and/or aspects,which is made with reference to the drawings, a brief description ofwhich is provided next.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the disclosure will becomeapparent upon reading the following detailed description and uponreference to the drawings.

FIG. 1 illustrates an example display system suitable for participationand correction by the optical correction systems and methods disclosed;

FIG. 2 is a system block diagram of an optical correction system;

FIG. 3 is a high level functional block diagram of location calibrationfor an optical correction method;

FIG. 4 illustrates a high level example one or more calibration patternsaccording to an embodiment;

FIG. 5 illustrates a specific example variation of the methodillustrated in FIG. 3 ; and

FIG. 6 illustrates a specific example of one or more calibrationpatterns represented by FIG. 4 .

While the present disclosure is susceptible to various modifications andalternative forms, specific embodiments or implementations have beenshown by way of example in the drawings and will be described in detailherein. It should be understood, however, that the disclosure is notintended to be limited to the particular forms disclosed. Rather, thedisclosure is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of an invention as defined by theappended claims.

DETAILED DESCRIPTION

Many modern display technologies suffer from defects, variations, andnon-uniformities, from the moment of fabrication, and can suffer furtherfrom aging and deterioration over the operational lifetime of thedisplay, which result in the production of images which deviate fromthose which are intended. Optical correction systems and methods can beused, either during fabrication or after a display has been put intouse, to measure and correct pixels (and sub-pixels) whose outputluminance varies from the expected luminance. AMOLED panels inparticular are characterized by luminance non-uniformity.

To correct for this intrinsic non-uniformity of the display, theincoming video signal is deliberately modified with compensation data orcorrection data such that it compensates for the non-uniformity. In someapproaches, to obtain the correction data the luminance of eachindividual panel pixel is measured for a range of greyscale luminancevalues, and correction values for each pixel are determined. A typicaloptical correction setup utilizes a monochrome or conventional RGB stillpicture camera as the measurement device. Display test patterns aredisplayed on the display and captured with the camera. Measurements inthe form of captured images are then processed to extract the actualluminance of each individual pixel of the display. Taking into accountthe greyscale luminance value of the pixel of the display test patternwhich was used to drive the pixel of the display, a correction signalfor that pixel of the display driven at that greyscale luminance valueis determined. Typically, accurate measurement of each pixel's luminanceor intensity relies upon an accurate determination of the location ofthe actual pixels of the panel (panel domain) within the captured imagestaken by the camera (image domain). Such location information allowsunambiguous attribution of intensity measured within various pixels ofthe captured test images to specific individual pixels of the displaypanel as its origin. As displays are produced with increasingly higherand higher resolutions this poses a problem for obtaining reliablecorrection data which rely on high precision identification of the panelpixel locations within captured test images (image domain).

In order to provide precise display panel pixel locations in the imagedomain for use in processing the various captured images of testpatterns displayed on the panel, one or more location calibrationpatterns specifically suited for determining accurate pixel locations inthe image domain are generated, displayed, captured by the camera, andthe resulting calibration images are then processed. The calibrationpatterns include a sparse or coarse distribution of panel features inthe panel domain for display and capture, and which enable processingand determination of a coarse functional estimate which maps orestimates every display panel pixel location to corresponding estimatedlocations within the calibration image, up to a coarse level ofaccuracy. The first distribution in the panel domain is sufficientlyunique and robust such that no specific prior location information isrequired to identify images of each of these features uniquely in thecalibration image domain. The calibration patterns also include a denseor fine distribution of display features for display and capture. Thisfine distribution need not be as sufficiently unique nor robust as thefirst distribution, nor sufficiently and uniquely identifiable in theimage domain absent any further information. However, each of thedisplay features (in the panel domain) of the second distribution can besufficiently and uniquely identified in the image domain with use of thecoarse functional estimate to approximate the fine features' locationsin the image domain. The estimated approximations of the fine features'locations are matched with the nearest detected fine features in theimage domain.

The locations of the fine features of the second distribution in theimage domain, once matched with coordinates of the same features in thepanel domain, are then processed to generate a precise high-resolutionfunctional estimate or mapping of all panel pixel locations in the imagedomain which is ultimately used in the processing of the captured testimages of the various display test patterns. This iterative process mayutilize more than two distributions of differing density or granularity,each providing the level of accuracy in feature location estimation touniquely discern and approximately locate, and then match the featuresof the next distribution. The various distributions may be embedded inone or more calibration patterns.

It should be understood that since individual panel pixels and featuresare not one dimensional points but are finite in size, any reference toa “location”, “position” or the “coordinates” thereof, is implicitly areference to a point location, position, or coordinate relative to andassociated therewith. In some embodiments, this is taken as the centroidof the panel pixel or feature, while in others, any other well definedand consistently applied relative standard point may be used. It shouldbe understood that references to “positions”, “locations”, or“coordinates” of pixels or features “in the panel domain” are equivalentto references to actual positions, locations, or coordinates of pixelsor features within calibration patterns displayed by the panel. It alsoshould be understood that references to “positions”, “locations”, or“coordinates” of pixels or features “in the image domain” are equivalentto references to actual “positions”, “locations”, or “coordinates” ofimages of pixels or features within the calibration images taken by thecamera.

While the embodiments described herein will be in the context of AMOLEDdisplays it should be understood that the optical correction systems andmethods described herein are applicable to any other display comprisingpixels, including but not limited to light emitting diode displays(LED), electroluminescent displays (ELD), organic light emitting diodedisplays (OLED), plasma display panels (PSP), microLED or quantum dotdisplays, among other displays.

It should be understood that the embodiments described herein pertain tosystems and methods of optical correction and compensation and do notlimit the display technology underlying their operation and theoperation of the displays in which they are implemented. The systems andmethods described herein are applicable to any number of various typesand implementations of various visual display technologies.

FIG. 1 is a diagram of an example display system 150 participating inthe methods and systems described further below in conjunction with anarrangement with a camera and optical correction processing. The displaysystem 150 includes a display panel 120, an address driver 108, a datadriver 104, a controller 102, and a memory storage 106.

The display panel 120 includes an array of pixels 110 (only oneexplicitly shown) arranged in rows and columns. Each of the pixels 110is individually programmable to emit light with individuallyprogrammable luminance values. The controller 102 receives digital dataindicative of information to be displayed on the display panel 120. Thecontroller 102 sends signals 132 to the data driver 104 and schedulingsignals 134 to the address driver 108 to drive the pixels 110 in thedisplay panel 120 to display the information indicated. The plurality ofpixels 110 of the display panel 120 thus comprise a display array ordisplay screen adapted to dynamically display information according tothe input digital data received by the controller 102. The displayscreen and various subsets of its pixels define “display areas” whichmay be used for monitoring and managing display brightness. The displayscreen can display images and streams of video information from datareceived by the controller 102. The supply voltage 114 provides aconstant power voltage or can serve as an adjustable voltage supply thatis controlled by signals from the controller 102. The display system 150can also incorporate features from a current source or sink (not shown)to provide biasing currents to the pixels 110 in the display panel 120to thereby decrease programming time for the pixels 110.

For illustrative purposes, only one pixel 110 is explicitly shown in thedisplay system 150 in FIG. 1 . It is understood that the display system150 is implemented with a display screen that includes an array of aplurality of pixels, such as the pixel 110, and that the display screenis not limited to a particular number of rows and columns of pixels. Forexample, the display system 150 can be implemented with a display screenwith a number of rows and columns of pixels commonly available indisplays for mobile devices, monitor-based devices, and/orprojection-devices. In a multichannel or color display, a number ofdifferent types of pixels, each responsible for reproducing color of aparticular channel or color such as red, green, or blue, will be presentin the display. Pixels of this kind may also be referred to as“subpixels” as a group of them collectively provide a desired color at aparticular row and column of the display, which group of subpixels maycollectively also be referred to as a “pixel”.

The pixel 110 is operated by a driving circuit or pixel circuit thatgenerally includes a driving transistor and a light emitting device.Hereinafter the pixel 110 may refer to the pixel circuit. The lightemitting device can optionally be an organic light emitting diode, butimplementations of the present disclosure apply to pixel circuits havingother electroluminescence devices, including current-driven lightemitting devices and those listed above. The driving transistor in thepixel 110 can optionally be an n-type or p-type amorphous siliconthin-film transistor, but implementations of the present disclosure arenot limited to pixel circuits having a particular polarity of transistoror only to pixel circuits having thin-film transistors. The pixelcircuit 110 can also include a storage capacitor for storing programminginformation and allowing the pixel circuit 110 to drive the lightemitting device after being addressed. Thus, the display panel 120 canbe an active matrix display array.

As illustrated in FIG. 1 , the pixel 110 illustrated as the top-leftpixel in the display panel 120 is coupled to a select line 124, a supplyline 126, a data line 122, and a monitor line 128. A read line may alsobe included for controlling connections to the monitor line. In oneimplementation, the supply voltage 114 can also provide a second supplyline to the pixel 110. For example, each pixel can be coupled to a firstsupply line 126 charged with Vdd and a second supply line 127 coupledwith Vss, and the pixel circuits 110 can be situated between the firstand second supply lines to facilitate driving current between the twosupply lines during an emission phase of the pixel circuit. It is to beunderstood that each of the pixels 110 in the pixel array of the display120 is coupled to appropriate select lines, supply lines, data lines,and monitor lines. It is noted that aspects of the present disclosureapply to pixels having additional connections, such as connections toadditional select lines, and to pixels having fewer connections.

With reference to the pixel 110 of the display panel 120, the selectline 124 is provided by the address driver 108, and can be utilized toenable, for example, a programming operation of the pixel 110 byactivating a switch or transistor to allow the data line 122 to programthe pixel 110. The data line 122 conveys programming information fromthe data driver 104 to the pixel 110. For example, the data line 122 canbe utilized to apply a programming voltage or a programming current tothe pixel 110 in order to program the pixel 110 to emit a desired amountof luminance. The programming voltage (or programming current) suppliedby the data driver 104 via the data line 122 is a voltage (or current)appropriate to cause the pixel 110 to emit light with a desired amountof luminance according to the digital data received by the controller102. The programming voltage (or programming current) can be applied tothe pixel 110 during a programming operation of the pixel 110 so as tocharge a storage device within the pixel 110, such as a storagecapacitor, thereby enabling the pixel 110 to emit light with the desiredamount of luminance during an emission operation following theprogramming operation. For example, the storage device in the pixel 110can be charged during a programming operation to apply a voltage to oneor more of a gate or a source terminal of the driving transistor duringthe emission operation, thereby causing the driving transistor to conveythe driving current through the light emitting device according to thevoltage stored on the storage device.

Generally, in the pixel 110, the driving current that is conveyedthrough the light emitting device by the driving transistor during theemission operation of the pixel 110 is a current that is supplied by thefirst supply line 126 and is drained to a second supply line 127. Thefirst supply line 126 and the second supply line 127 are coupled to thevoltage supply 114. The first supply line 126 can provide a positivesupply voltage (e.g., the voltage commonly referred to in circuit designas “Vdd”) and the second supply line 127 can provide a negative supplyvoltage (e.g., the voltage commonly referred to in circuit design as“Vss”). Implementations of the present disclosure can be realized whereone or the other of the supply lines (e.g., the supply line 127) isfixed at a ground voltage or at another reference voltage.

The display system 150 also includes a monitoring system 112. Withreference again to the pixel 110 of the display panel 120, the monitorline 128 connects the pixel 110 to the monitoring system 112. Themonitoring system 12 can be integrated with the data driver 104, or canbe a separate stand-alone system. In particular, the monitoring system112 can optionally be implemented by monitoring the current and/orvoltage of the data line 122 during a monitoring operation of the pixel110, and the monitor line 128 can be entirely omitted. The monitor line128 allows the monitoring system 112 to measure a current or voltageassociated with the pixel 110 and thereby extract information indicativeof a degradation or aging of the pixel 110 or indicative of atemperature of the pixel 110. In some embodiments, display panel 120includes temperature sensing circuitry devoted to sensing temperatureimplemented in the pixels 110, while in other embodiments, the pixels110 comprise circuitry which participates in both sensing temperatureand driving the pixels. For example, the monitoring system 112 canextract, via the monitor line 128, a current flowing through the drivingtransistor within the pixel 110 and thereby determine, based on themeasured current and based on the voltages applied to the drivingtransistor during the measurement, a threshold voltage of the drivingtransistor or a shift thereof.

The controller and 102 and memory store 106 together or in combinationwith a compensation block (not shown) use compensation data orcorrection data, in order to address and correct for the variousdefects, variations, and non-uniformities, existing at the time offabrication, and optionally, defects suffered further from aging anddeterioration after usage. In some embodiments, the correction dataincludes data for correcting the luminance of the pixels obtainedthrough measurement and processing using an external optical feedbacksystem such as that described below. Some embodiments employ themonitoring system 112 to characterize the behavior of the pixels and tocontinue to monitor aging and deterioration as the display ages and toupdate the correction data to compensate for said aging anddeterioration over time.

For the embodiments disclosed herein, correction data is directlydetermined during an optical correction operation either during orsubsequent to fabrication or after the display has been in operation forsome time, from observing the luminance of each pixel and determiningthe correction data to produce luminance of an acceptable level.

It should be understood that the display system 150 is only one exampleof a display system which may participate in the methods and systemsdescribed below.

Referring to FIG. 2 , an optical correction system 200 according to anembodiment will now be described.

The optical correction system 200 includes display system 250 which isto be corrected, a camera 230, a controller 202 for overall control ofthe process, which in the embodiment of FIG. 2 is shown as part of thedisplay system 250, an optical correction processing module 240 forcontrolling specific processes of the optical correction methods, andmemory storage 206 in the display system 250. The optical correctionprocessing 240 can be part of an external tool that is used for examplein a production factory for correction of the displays. In other cases,optical correction processing 240 can be part of the display systemand/or the controller, for example, integrated in a timing controllerTCON. The display system 250 of FIG. 2 may correspond more or less tothe display system 150 of FIG. 1 and includes similar componentsthereof, of which specifically, drivers 207, the display panel 220, thecontroller 202, and memory storage 206 are shown explicitly forconvenience.

The camera 230 is arranged to measure the luminance of all of the pixels110 of the display panel 220. The camera 230 may be operated manually orautomatically controlled by one or both of the controller 202 andoptical correction processing 240. The camera 230 generates a luminancemeasurement image representative of the optical output of the displaypanel 220, and the optical correction processing 240 receives theluminance measurement image data from the camera 230. Optical correctionprocessing 240 then processes the measurement image data to generate thecorrection data which are unique to each display panel 220 and stores itin memory storage 206 for use by the display system 250 in correctingthe luminance of the pixels of the display panel 220 when displayingimages.

The camera 230 may be based on a digital photography system with lenses,and may be a monochromatic digital camera or a standard digital camera,such as a monochromatic or RGB, CCD CMOS or other sensor array basedcamera, or any other suitable optical measurement technology capable oftaking optical images through a lens. Luminance measurement image datarefers to any matrix containing optical luminance data corresponding tothe output of the display panel 220, and may comprise multiple channelssuch as red (R), green (G), blue (B) etc. and in some cases may bemonochromatic as in the case where the camera 230 is monochromatic.Hereinafter, luminance measurement image data will be referred to simplyas a “captured image” and if monochromatic, will be assumed to includeone luminance value for every pixel of the captured image. It should beunderstood that any reference made to “greyscale luminance value” is areference to the signal data value used to program and drive a pixel andwhich results in a pixel producing an actual luminance. For simplicity,the preset luminance values associated with the various pixel patternsdescribed below are characterized in terms of the correspondinggreyscale luminance value which is used to program and drive the pixels.Advantages of using a monochromatic camera versus an RGB camera includefaster exposure times, avoidance of display and sensor R,G,B frequencymismatch, aliasing, and/or crosstalk, avoidance of mismatching numbersor arrangements of the R,G,B sub-pixels of the display and the R,G,Belements of the sensor array, and ease of handling yellow or whitesubpixels of display panel 220. In some embodiments utilizing either amonochromatic or an RGB camera, measurements occur while the displayonly displays a single channel, primary color, or subpixel color (R, G,B, Y, or W etc.) at any one time.

With reference also to the location calibration for an opticalcorrection method 300 of FIG. 3 , the camera 230 is arranged 302 infront of the display panel 220 and one or more calibration patterns aregenerated or retrieved and provided to the display panel 220 fordisplay, while the camera 230 which has been arranged 302 in front ofthe display panel 220, captures one or more calibration images of theone or more calibration patterns 304. The camera 230 and the displaypanel 220 are arranged 302 such that the entirety of the viewable areaof the display panel 220 appears within the field of view of the camera230. In some embodiments, the camera 230 is positioned in front ofdisplay panel 220, aimed at the center of the viewable area of thedisplay panel 220 and with the viewable area of the display panel 220maximized to occupy as much of the field of view of the camera 230 aspossible. The line of sight of the camera 230 (controlled by camera pan,tilt, and positioning) may be such that it is parallel and coincidentwith a normal to the plane of the front surface of the display panel 220emerging at the center of the display panel 220 to reduce distortionsand to ensure any remaining distortions are as symmetrical as possiblein the resulting images of the display panel 220.

With reference also to the high level example of one or more calibrationpatterns according to an embodiment 400 of FIG. 4 , the display 450displays on the display panel 420 one or more calibration patternsincluding a sparse or coarse distribution of display features 402. Thesparse or coarse distribution of display features (also referred toherein as coarse features) are relatively widely separated within theone or more calibration patterns and include pixels which are coloredwith a foreground color or otherwise colored differently from abackground color of the calibration pattern. In some embodiments thecoarse features 402 include white pixels. In some embodiments thebackground is black, causing corresponding pixels of the display toremain substantially unlit. The pattern of the coarse features 402should be robust and unique enough to ensure that occasional flaws inthe display panel, such as bad pixels, whether dead, stuck, orotherwise, will not prevent the optical correction processing 240 fromfinding and correctly and uniquely identifying most of the coarsefeatures 402 in the one or more calibration images (hereinafter“calibration images”). Hereinafter, “identifying” a feature (i.e. animage of a feature) in a calibration image, means to match thatfeature's image in that calibration image with the actual feature of thecalibration pattern.

The coarse features 402 may be arranged in a regular or non-regularpattern and depending on the application and particular display type,may have locations with an average two dimensional density which variesin different areas within the display panel. For flat panel displayswith a homogenous density a constant density regular pattern may beused. In some embodiments the coarse features 402 may be arranged in arectilinear or other regular array. The locations of the coarse features402 are generally spaced from the periphery of the display panel toavoid potential manufacturing flaws which tend to afflict those areasmore than areas closer to the center of the display. Each of the coarsefeatures are visually discernable within the calibration images andsince they are generated by specific arrangements of actual pixelswithin the display panel, they can be processed to determine panel pixellocation information, in some cases taking the form of a centroid of asingle pixel within with the coarse feature 402. Although represented bysmall circles in FIG. 4 , it is to be understood that the actual pixelarrangements of each coarse feature may take on any form which issufficiently recognizable within the calibration images and which can beprocessed for sufficient panel pixel location information accuracy tounambiguously locate fine features within the calibration images (seediscussion below). In some embodiments the coarse features include, asingle pixel, lines, crosses, filled or hollow circles, squares, orrectangles, or any other shape, and for ease of locating within thecalibration images, and to ensure the particular shape is notcompromised, may include a surrounding area which is occupied by thebackground or otherwise absent any other coarse or fine features, andmay, for example, impose an interruption in an otherwise homogenousdensity in the pattern of the fine features.

The coarse features 402 are identified in the calibration images and theimage locations of those features within the calibration images alongwith the known locations of those features within the calibrationpatterns are used to generate an estimate of the display panel pixellocations 306 within the calibration images. This estimate may take theform of an algorithm, function, matrix, look up table or any otherprocessing which assigns or maps 2D locations of the pixels of thedisplay panel to their estimated 2D locations in the calibration images.Generally speaking, this estimate may be used as a mapping between thelocations of actual pixels of the display panel and coarse estimates oftheir corresponding locations within the calibration images. Due to theinevitable differences in resolution and alignment, the locations of theactual panel pixels generally will not coincide with the locations ofthe pixels of the calibration image, and hence the estimates for thelocations (coarse or otherwise) generally also will not coincide withthe locations of the pixels of the calibration image. Position estimatesfor the panel pixels therefore include subpixel accuracy whetherexpressed in terms of coordinate positions within the calibration imageor on some other normalized scale in each dimension within thecalibration image. This coarse estimate generated by the opticalcorrection processing 240, since it is generated from the coarsefeatures provides a low-resolution estimate. Here, low-resolution is nota reference to the numerical or bit-wise precision of the valuesproduced by the estimate, but instead characterizes known limits of itsaccuracy. In other words, the coarse estimate is low-resolution in thatit is known only to be accurate up to a relatively low numericalprecision or bit-depth.

The display 450 displays on the display panel 420 calibration patternsalso including a dense or fine distribution of display features 404. Thedense or fine distribution of display features (also referred to hereinas fine features 404) are relatively closely separated within thecalibration pattern, being generally spaced apart at an average spacingwhich is smaller than the average spacing of the coarse features 402.The fine features 404 include pixels which are colored with a foregroundcolor or otherwise colored differently from the background color of thecalibration pattern. In some embodiments the fine features 404 includewhite pixels.

The coarse estimate for the panel pixel locations is then used to locate308 the fine features 404 of the calibration images. The opticalcorrection processing 240 determines the expected positions within thecalibration image of each of the fine features 404 using the coarseestimate and the known locations of the fine features 404 within thecalibration patterns, in order to identify images of the fine features404. Due to the low resolution of the estimate, in some embodiments, theimage of a fine feature will often not exactly overlap the expectedposition of that fine feature. In some embodiments, the closest finefeature image to a particular fine feature's expected position withinthe calibration image is identified as corresponding to that particularfine feature 404. In some embodiments, if the identified fine featureimage is not found within a certain threshold distance from a particularfine feature's expected position, it is discarded. In some embodiments,only a distance from a fine feature's expected position up to thethreshold distance is searched, and a fine feature image is identifiedas corresponding to that fine feature only if that image falls withinthat distance and is the closest.

The spacing of the pattern of the fine features 404 should be largeenough to match the accuracy of the coarse estimate but small enough toprovide a high-resolution estimate once processed. Specifically, thespacing should be sufficiently large so that the accuracy of the coarseestimate can correctly and uniquely identify each of the fine features404 in the calibration images. If the spacing is too small, the coarseestimates of the positions of the fine features 404 risk misidentifyingfine features 404 within the calibration images. Given that the amountof available information and the accuracy of the high-resolutionestimate once processed increases with the total number of fine features404 within the calibration images, the spacing is generally chosen to beas small as possible while being sufficiently large for properidentification by the coarse estimate.

The fine features 404 may be arranged in a regular or non-regularpattern and depending on the application and particular display type,may have locations with an average two dimensional density which variesin different areas within the display panel. For flat panel displayswith a homogenous density a constant density regular pattern may beused. In some embodiments the fine features 404 may be arranged in arectilinear or other regular array such as the triangular array depictedin FIG. 4 . In some embodiments the fine features 404 are distributedthroughout the entire display area. Each of the fine features 404 arevisually discernable within the calibration images and since they aregenerated by specific arrangements of actual pixels within the displaypanel, they can be processed to determine panel pixel locationinformation, in some cases taking the form of a centroid of a singlepixel within with the fine feature 404. Although represented by smalldots in FIG. 4 , it is to be understood that the actual pixelarrangements of each fine feature 404 may take on any form which issufficiently recognizable within the calibration images and which can beprocessed for sufficient panel pixel location information accuracy togenerate a high-resolution estimate of the locations of the panel pixelswithin the calibration images. The fine features generally are small insize, consisting of a relatively small number of pixels, to enable thedesired density to produce the high-resolution estimate. In someembodiments, the fine features include, lines, crosses, filled or hollowcircles or squares or rectangles, or any other shape, and for ease oflocating within the calibration images, and to ensure the particularshape is not compromised, is sufficiently spaced apart from otherfeatures, both coarse and fine. In some embodiments, the fine featuresare single-pixels.

The image locations of the fine features 404 within the calibrationimages along with the known locations of those features within thecalibration patterns are used to generate a high-resolution estimate ofthe display panel pixel locations 310 within the calibration images.This estimate may take the form of an algorithm, function, matrix, lookup table or any other processing which assigns or maps 2D locations ofthe pixels of the display panel to their estimated 2D locations in thecalibration image and may or may not be an estimate similar in kind tothe coarse estimate. Generally speaking, this estimate may be used as amapping between the locations of actual pixels of the display panel andhigh-resolution estimates of their corresponding locations within thecalibration images. High-resolution position estimates for locations ofthe panel pixels include subpixel accuracy whether expressed in terms ofcoordinate positions within the calibration image or on some othernormalized scale in each dimension within the calibration image. Thishigh-resolution estimate generated by the optical correction processing,since it is generated from the fine features which outnumber the coarsefeatures and which provides more position information than the coarsefeatures, is a more accurate estimate than the coarse estimate. Here,high-resolution is not a reference to the numerical or bit-wiseprecision of the values produced by the estimate, but insteadcharacterizes known limits of its accuracy. In other words, thehigh-resolution estimate is high-resolution in that it is known to beaccurate up to a relatively high numerical precision or bit-depth.

Once the high-resolution estimate has been generated, optical correctionprocessing 240 can properly process the captured test images containingthe luminance measurements used to generate the correction data whichwill be used to correct images displayed by the display panel. Asdescribed above, accurate measurement of each pixel's luminance orintensity relies upon an accurate determination of the locations of theactual pixels of the display within the captured images taken by thecamera, and the high-resolution estimate provides this.

Either before, during, or after display and capture of the calibrationpatterns 304, test patterns are displayed on the display panel andcaptured by the camera generating test images 312.

The test images are then processed to determine correction data usingthe high-resolution estimate of the display panel pixel locationspreviously generated, in order to accurately attribute measuredintensities within the test images to the proper panel pixels from whichthey originate 314. In some embodiments, the test images are processedby using the high-resolution estimates of the panel pixel locationswithin the test images and an integration window around each of thoselocations within the test images to calculate the intensity of the panelpixels. This data is processed to calculate the correction data orcalibration factors.

In order to correct the display of images displayed by the panel,specifically, in order to create a more uniform display, the correctiondata or calibration factors are transferred to the memory storage of thedisplay 316, and the display corrects the display image data using thestored correction data 318 to display images which have been correctedand hence exhibit improved uniformity.

In some embodiments where the display only displays a single channel,primary color, or subpixel color (R, G, B, Y, or W etc.) at any onetime, the method is performed separately for each channel, primarycolor, or subpixel color (R, G, B, Y, or W etc.).

It should be understood that this iterative process of using aparticular pattern of features of one level of granularity within thecalibration patterns to generate one estimate of a particular resolutionwhich is then used to find and identify features of another pattern offeatures of a finer level of granularity within the calibration patternsto generate another estimate of a higher resolution, is not limited totwo levels of granularity and two levels of estimate resolution. In someembodiments any number of two or more levels of granularity, i.e.calibration patterns having two or more kinds of features each arrangedin increasingly finer or denser distributions may be used tosuccessively generate estimates of increasingly higher resolution forfinding the next successive set of features.

It also should be understood that in some embodiments the one or morecalibration patterns is a single calibration pattern including all kindsor granularities of features while in other embodiments the one or morecalibration patterns include more than one pattern, preferably eachpattern including only one kind or granularity level of feature.Advantageously, in embodiments in which the one or more calibrationpatterns is a single calibration pattern, time is saved by reducing thenumber of calibration patterns to be displayed to a single calibrationpattern and by reducing the number of calibration images to be capturedto a single calibration image

With reference also to the specific example variation illustrated inFIG. 5 of the location calibration for an optical correction method 300of FIG. 3 , the camera 230 is arranged in front of the display panel 220and calibration patterns are generated or retrieved and provided to thedisplay panel 220 for display, while the camera 230 captures calibrationimages of the calibration patterns 502.

With reference also to the specific example calibration patterns 600illustrated in FIG. 6 , the display 650 displays on the display panel620 calibration patterns including a sparse or coarse distribution ofdisplay features 602. The sparse or coarse distribution of displayfeatures (also referred to herein as coarse features) are relativelywidely separated within the calibration patterns and include pixelswhich are colored with a foreground color or otherwise coloreddifferently from a background color of the calibration patterns. In someembodiments, the coarse features 602 include white pixels. In someembodiments, the background is black, causing corresponding pixels ofthe display to remain substantially unlit. The pattern of the coarsefeatures 602 is robust and unique enough to ensure that occasional flawsin the display panel, such a bad pixels, whether dead, stuck, orotherwise, will not prevent the optical correction processing 240 fromfinding and correctly and uniquely identifying most of the coarsefeatures 602 in the calibration images.

The coarse features 602 are arranged in a regular rectilinear patternconstituting a distribution of homogeneous density within the displaypanel. In FIG. 6 a 3×4 array is used for illustration only, generallyarrays of other (and often higher) dimensions are used, which areappropriate for the dimensions of the particular display, and forattaining a coarse estimate of the required accuracy to process the finefeatures. The locations of the coarse features 602 are spaced from theperiphery of the display panel to avoid potential manufacturing flawswhich tend to afflict those areas more than areas closer to the centerof the display. Each of the coarse features 602 are visually discernablewithin the calibration images to the optical correction processing 240and since they are generated by specific arrangements of actual pixelswithin the display panel, they can be processed to determine panel pixellocation information. In this embodiment, each coarse feature 602includes a single pixel 603 surrounded by a square area of unlit orbackground color pixels, i.e. absent any other coarse or fine features,and can be processed to determine panel pixel location information inthe form of a centroid of a single lit or foreground color pixel 603 atthe center of each coarse feature 602. These square areas impose aninterruption in an otherwise homogenous density in the pattern of thefine features. The size and shape of the square area surrounding thesingle pixel 603 should be sufficient to meet the requirements ofuniqueness, robustness, and being discernable to the optical correctionprocessing 240 mentioned above, and in some embodiments is a square of adimension multiple times larger than the spacing of the fine features604. The coarse features in the calibration images are located 504 byoptical correction processing 240. In some embodiments, the opticalcorrection processing 240 discerns each coarse feature 602 by findinglit or foreground color pixels in the calibration image which do nothave neighbors within some distance below a threshold related to thesize of the blank square area (generally about ½ of the length of a sideof the square). Those lit or foreground pixels in the calibrated imagesare determined to be the images of the single pixels 603 of the coarsefeatures 602, and along with the known locations of those featureswithin the calibration patterns, are used to generate a coarse estimateof the display panel pixel locations 506 within the calibration images.

This estimate may take the form of an algorithm, function, matrix, lookup table or any other processing which assigns or maps 2D locations ofthe pixels of the display panel to their estimated 2D locations in thecalibration image. This estimate may be used as a mapping between thelocations of actual pixels of the display panel and coarse estimates oftheir corresponding locations within the calibration images. In someembodiments the coarse estimate takes the form a low-order 2-Dpolynomial. The order of the low-order polynomial depends upon a numberof factors but in general it should not be too low or too high. When itis too low inaccuracy increases and the coarse estimate will not beappropriate for the spacing of the fine features 604. When it is toohigh, anomalies may be introduced or noise in the measurements amplifiedand so forth. Ideally the order is sufficient for locating the finefeatures 604 accurately and includes some automatic filtering out ofnoise. In some embodiments the order of the low-order polynomial is 2.This coarse estimate generated by the optical correction processing 240,since it is generated from the coarse features 602 and is a low-orderpolynomial provides a low-resolution estimate. Here, low-resolution isnot a reference to the numerical or bit-wise precision of the valuesproduced by the estimate, but instead characterizes known limits of itsaccuracy. In other words, the coarse estimate is low-resolution in thatit is known only to be accurate up to a relatively low numericalprecision or bit-depth.

The display 650 displays on the display panel 620 calibration patternsalso including a dense or fine distribution of display features 604. Thedense or fine distribution of display features (also referred to hereinas fine features 604) are relatively closely separated within thecalibration patterns, being generally spaced apart at an average spacingwhich is smaller than the average spacing of the coarse features 602.The fine features 604 include pixels which are colored with a foregroundcolor or otherwise colored differently from the background color of thecalibration patterns. In some embodiments each fine feature 604 includesa single white pixel.

The coarse estimate for the panel pixel locations is then used to locatethe fine features 604 of the calibration images. First, the opticalcorrection processing 240 determines the expected positions within thecalibration images of each of the fine features 604 using the coarseestimate 508 and the known locations of the fine features 404 within thecalibration patterns, in order to identify images of the fine features604. Due to the low resolution of the estimate, the image of a finefeature will often not exactly overlap the expected position of thatfine feature. Hence, the optical correction processing 240 proceeds tolocate the fine feature image closest to each fine feature's expectedposition 510 within the calibration images to identify it as the finefeature image corresponding to that particular fine feature 604. In someembodiments, if the identified fine feature image is not found within acertain threshold distance from a particular fine feature's expectedposition, it is discarded. In some embodiments, only a distance from afine feature's expected position up to the threshold distance issearched, and a fine feature image is identified as corresponding tothat fine feature only if that image falls within that distance and isthe closest.

The spacing of the pattern of the fine features 604 should be largeenough to match the accuracy of the coarse estimate but small enough toprovide a high-resolution estimate once processed. Specifically, thespacing should be sufficiently large so that the accuracy of the coarseestimate can correctly and uniquely identify each of the fine features604 in the calibration images. If the spacing is too small, the coarseestimates of the positions of the fine features 604 risk misidentifyingfine features 604 within the calibration images. Given that the amountof available information and the accuracy of the high-resolutionestimate once processed increase with the total number of fine features604 within the calibration images, the spacing is generally chosen to beas small as possible while being sufficiently large for properidentification by the coarse estimate.

The fine features 604 are arranged in a regular rectilinear patternconstituting a distribution of homogeneous density within the displaypanel and are distributed throughout the entire display area. In FIG. 6, the specific fine array is used for illustration only, generallyarrays of any suitable pattern and dimensions are used, which areappropriate for the dimensions of the particular display, and forattaining the high-resolution estimate of the desired accuracy. In someembodiments, a rectangular array of single lit or foreground pixels atevery 10th row and column panel pixel position is used. Each of the finefeatures 604 are visually discernable within the calibration images andsince they are generated by specific arrangements of actual pixelswithin the display panel, they can be processed to determine panel pixellocation information. In this embodiment, each fine features 604 aresingle-pixels. Locations of the images of the fine features 604, located510 from the expected positions using the coarse estimate, along withthe known locations of the fine features 604 within the calibrationpatterns, are used to generate a high-resolution estimate of the displaypanel pixel locations 512 within the calibration images.

The high-resolution estimate may take the form of an algorithm,function, matrix, look up table or any other processing which assigns ormaps 2D locations of the pixels of the display panel to their estimated2D locations in the calibration image and may or may not be an estimatesimilar in kind to the coarse estimate. This estimate may be used as amapping between the locations of actual pixels of the display panel andhigh-resolution estimates of their corresponding locations within thecalibration images. In some embodiments the high-resolution estimate isa 2D high-order polynomial. The order of the high order polynomialdepends upon a number of factors but in general it should not be too lowor too high. When it is too low inaccuracy increases and thehigh-resolution estimate will not be appropriate for accuratelydetermining the positions of the test pixel locations within the testimages. When it is too high, anomalies may be introduced or noise in themeasurements amplified and so forth. Ideally it is an order sufficientfor locating the panel pixel locations in the test images with highaccuracy and yet includes some automatic filtering out of noise. In someembodiments the order of the high-order polynomial is 7. High-resolutionposition estimates for locations of the panel pixels include subpixelaccuracy whether expressed in terms of coordinate positions within thecalibration image or on some other normalized scale in each dimensionwithin the calibration image. This high-resolution estimate generated bythe optical correction processing 512, since it is generated from thefine features which outnumber and are more closely spaced than thecoarse features, provides more position information than the coarsefeatures and is a more accurate estimate than the coarse estimate. Here,high-resolution is not a reference to the numerical or bit-wiseprecision of the values produced by the estimate, but insteadcharacterizes known limits of its accuracy. In other words, thehigh-resolution estimate is high-resolution in that it is known to beaccurate up to a relatively high numerical precision or bit-depth.

Once the high-resolution estimate has been generated, optical correctionprocessing 240 can properly process the captured test images containingthe luminance measurements used to generate the correction data whichwill be used to correct images displayed by the display panel. Asdescribed above, accurate measurement of each pixel's luminance orintensity relies upon an accurate determination of the expectedlocations of the actual pixels of the display panel within the capturedimages taken by the camera, and the high-resolution estimate providesthis 514.

In this embodiment two levels of granularity and two levels of estimateresolution are utilized. In some embodiments the one or more calibrationpatterns is a single calibration pattern including both the coarsefeatures 602 and fine features 604 as illustrated in FIG. 6 .Advantageously, in such embodiments, time is saved by reducing thenumber of calibration patterns to be displayed to a single calibrationpattern and the reducing the number of calibration images to be capturedto a single calibration image.

In some embodiments where the display only displays a single channel,primary color, or subpixel color (R, G, B, Y, or W etc.) at any onetime, the method is performed separately for each channel, primarycolor, or subpixel color (R, G, B, Y, or W etc.).

Any of the methods, algorithms, implementations, or procedures describedherein can include machine-readable instructions for execution by: (a) aprocessor, (b) a controller, and/or (c) any other suitable processingdevice or circuit. Any algorithm, software, or method disclosed hereincan be embodied in software stored on a non-transitory tangible mediumsuch as, for example, a flash memory, a CD-ROM, a floppy disk, a harddrive, a digital versatile disk (DVD), or other memory devices, butpersons of ordinary skill in the art will readily appreciate that theentire algorithm and/or parts thereof could alternatively be executed bya device other than a controller and/or embodied in firmware ordedicated hardware in a well-known manner (e.g., it may be implementedby an application specific integrated circuit (ASIC), a programmablelogic device (PLD), a field programmable logic device (FPLD), discretelogic, etc.). Also, some or all of the machine-readable instructionsrepresented in process described herein can be implemented manually asopposed to automatically by a controller, processor, or similarcomputing device or machine. Further, although specific algorithms orprocesses have been described, persons of ordinary skill in the art willreadily appreciate that many other methods of implementing the examplemachine readable instructions may alternatively be used. For example,the order of execution of some of the steps may be changed, and/or someof the blocks described may be changed, eliminated, or combined.

While particular implementations and applications of the presentdisclosure have been illustrated and described, it is to be understoodthat the present disclosure is not limited to the precise constructionand compositions disclosed herein and that various modifications,changes, and variations can be apparent from the foregoing descriptionswithout departing from the spirit and scope of an invention as definedin the appended claims.

What is claimed is:
 1. An optical correction method for correctingdisplay of images on a display panel having pixels, the methodcomprising: displaying one or more calibration patterns on the displaypanel while capturing one or more calibration images of said calibrationpatterns, said one or more calibration patterns comprising a pattern ofcoarse features and a pattern of fine features, an average spatialdensity of the coarse features less than an average spatial density ofthe fine features; locating images of the fine features within thecalibration images with use of the images of the coarse features in thecalibration images; and generating correction data for correcting imagesdisplayed in the display panel with use of the located images of thefine features.
 2. The optical correction method of claim 1, whereinlocating images of the fine features within the calibration images withuse of the images of the coarse features in the calibration imagesfurther comprises: generating a coarse estimate of panel pixel locationswithin the calibration images from the images of the coarse features inthe calibration images; and locating images of the fine features withinthe calibration images with use of the coarse estimate.
 3. The opticalcorrection method of claim 2, wherein generating correction data forcorrecting images displayed in the display panel with use of the locatedimages of the fine features further comprises: generating ahigh-resolution estimate of panel pixel locations within the calibrationimages from the located images of the fine features in the calibrationimages, the high-resolution estimate having greater accuracy than thecoarse estimate; and generating correction data for correcting imagesdisplayed in the display panel with use of the high-resolution estimate.4. The optical correction method of claim 1, wherein the one or morecalibration patterns comprises a single calibration pattern, and whereinthe once or more calibration images comprises a single image.
 5. Theoptical correction method of claim 1, wherein the coarse features arespaced apart from a periphery of the one or more calibration patterns.6. The optical correction method of claim 1, wherein the fine featuresare distributed throughout the one or more calibration patterns.
 7. Theoptical correction method of claim 1, wherein each fine feature includespixels of a foreground color, and each coarse feature includes pixels ofa foreground color surrounded by an area of a background color, saidarea absent other coarse features or fine features.
 8. The opticalcorrection method of claim 3, wherein the coarse estimate comprises afirst 2D polynomial function, the high-resolution estimate comprises asecond 2D polynomial function, and the second 2D polynomial function hasan order greater than an order of the first 2D polynomial function. 9.The optical correction method of claim 1, wherein the one or morecalibration patterns comprises a single calibration pattern and the onceor more calibration images comprises a single image, wherein the coarsefeatures are spaced apart from a periphery of the one or morecalibration patterns and include a single pixel of a foreground colorsurrounded by a square area of a background color, said square areaabsent other coarse features or fine features, wherein the fine featuresare distributed throughout the single calibration pattern and each finefeature includes a single pixel of a foreground color.
 10. The opticalcorrection method of claim 9, wherein locating images of the finefeatures within the calibration images with use of the images of thecoarse features in the calibration images further comprises: generatinga coarse estimate of panel pixel locations within the calibration imagesfrom the images of the coarse features in the calibration images, by:locating images of the coarse features in the single calibration image;identifying the coarse features of the single calibration patterncorresponding to said images of the coarse features; and generating acoarse mapping between panel pixel locations and calibration image pixellocations from locations of the images of the coarse features in thesingle calibration image and known locations of the coarse features inthe single calibration pattern; and locating images of the fine featureswithin the calibration images with use of the coarse estimate, by:estimating expected locations of images of the fine features within thesingle calibration image with use of the coarse estimate and knownlocations of the fine features in the single calibration pattern; andwherein generating correction data for correcting images displayed inthe display panel with use of the located images of the fine featuresfurther comprises: generating a high-resolution estimate of panel pixellocations within the calibration images from the located images of thefine features in the calibration images, the high-resolution estimatehaving greater accuracy than the coarse estimate, by: for each expectedlocation of an image of a fine feature, determining the closest image ofa fine feature in the single calibration image which falls within adistance threshold to identify the fine features of the singlecalibration pattern corresponding to said images of the fine features;and generating a high-resolution mapping between panel pixel locationsand calibration image pixel locations from locations of the images ofthe fine features in the single calibration image and known locations ofthe fine features in the single calibration pattern; and generatingcorrection data for correcting images displayed in the display panelwith use of the high-resolution estimate.
 11. An optical correctionsystem for correcting display of images on a display panel havingpixels, the system comprising: an optical measurement device arranged tooptically measure the display panel; an optical processing circuitcoupled to said optical measurement device adapted to display one ormore calibration patterns on the display panel while capturing one ormore calibration images of said calibration patterns with said opticalmeasurement device, said one or more calibration patterns comprising apattern of coarse features and a pattern of fine features, an averagespatial density of the coarse features less than an average spatialdensity of the fine features; locate images of the fine features withinthe calibration images with use of the images of the coarse features inthe calibration images; and generate correction data for correctingimages displayed in the display panel with use of the located images ofthe fine features.
 12. The optical correction system of claim 11,wherein the optical processing circuit is further adapted to locateimages of the fine features within the calibration images with use ofthe images of the coarse features in the calibration images, by:generating a coarse estimate of panel pixel locations within thecalibration images from the images of the coarse features in thecalibration images; and locating images of the fine features within thecalibration images with use of the coarse estimate.
 13. The opticalcorrection system of claim 12, wherein the optical processing circuit isfurther adapted to generate correction data for correcting imagesdisplayed in the display panel with use of the located images of thefine features, by: generating a high-resolution estimate of panel pixellocations within the calibration images from the located images of thefine features in the calibration images, the high-resolution estimatehaving greater accuracy than the coarse estimate; and generatingcorrection data for correcting images displayed in the display panelwith use of the high-resolution estimate.
 14. The optical correctionsystem of claim 11, wherein the one or more calibration patternscomprises a single calibration pattern, and wherein the once or morecalibration images comprises a single image.
 15. The optical correctionsystem of claim 11, wherein the coarse features are spaced apart from aperiphery of the one or more calibration patterns.
 16. The opticalcorrection system of claim 11, wherein the fine features are distributedthroughout the one or more calibration patterns.
 17. The opticalcorrection system of claim 11, wherein each fine feature includes pixelsof a foreground color, and each coarse feature includes pixels of aforeground color surrounded by an area of a background color, said areaabsent other coarse features or fine features.
 18. The opticalcorrection system of claim 13, wherein the coarse estimate comprises afirst 2D polynomial function, the high-resolution estimate comprises asecond 2D polynomial function, and the second 2D polynomial function hasan order greater than an order of the first 2D polynomial function. 19.The optical correction system of claim 11, wherein the one or morecalibration patterns comprises a single calibration pattern and the onceor more calibration images comprises a single image, wherein the coarsefeatures are spaced apart from a periphery of the one or morecalibration patterns and include a single pixel of a foreground colorsurrounded by a square area of a background color, said square areaabsent other coarse features or fine features, wherein the fine featuresare distributed throughout the single calibration pattern and each finefeature includes a single pixel of a foreground color.
 20. The opticalcorrection system of claim 19, wherein the optical processing circuit isfurther adapted to: locate images of the fine features within thecalibration images with use of the images of the coarse features in thecalibration images by: generating a coarse estimate of panel pixellocations within the calibration images from the images of the coarsefeatures in the calibration images, by: locating images of the coarsefeatures in the single calibration image; identifying the coarsefeatures of the single calibration pattern corresponding to said imagesof the coarse features; and generating a coarse mapping between panelpixel locations and calibration image pixel locations from locations ofthe images of the coarse features in the single calibration image andknown locations of the coarse features in the single calibrationpattern; and locating images of the fine features within the calibrationimages with use of the coarse estimate, by: estimating expectedlocations of images of the fine features within the single calibrationimage with use of the coarse estimate and known locations of the finefeatures in the single calibration pattern; and generate correction datafor correcting images displayed in the display panel with use of thelocated images of the fine features by: generating a high-resolutionestimate of panel pixel locations within the calibration images from thelocated images of the fine features in the calibration images, thehigh-resolution estimate having greater accuracy than the coarseestimate, by: for each expected location of an image of a fine feature,determining the closest image of a fine feature in the singlecalibration image which falls within a distance threshold to identifythe fine features of the single calibration pattern corresponding tosaid images of the fine features; and generating a high-resolutionmapping between panel pixel locations and calibration image pixellocations from locations of the images of the fine features in thesingle calibration image and known locations of the fine features in thesingle calibration pattern; and generating correction data forcorrecting images displayed in the display panel with use of thehigh-resolution estimate.